GCN Circular 7411
Subject
GRB 080310: ROTSE-III Observations of Optical Counterpart
Date
2008-03-12T03:32:31Z (16 years ago)
From
Fang Yuan at ROTSE <yuanfang@umich.edu>
F. Yuan (U Mich), R. Quimby (Caltech), H. Swan (U Mich), C. Akerlof (U
Mich), report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
080310 (Swift trigger 305288; Cummings et al., GCN 7382) and began
imaging at UT 08:38:25.7 (5.7 sec after the GCN notice time) under
cloudy conditions. The first usable image with a detection of the OT
(Chornock et al. GCN 7381) starts at UT 09:03:03.4. Observations
continued in fluctuating weather conditions until about 3 hours after
the trigger.
The OT is slightly blended with the two nearby stars in ROTSE images. To
reduce the contamination, we tried two different methods to obtain the
OT magnitudes, first by subtracting the scaled PSF of the two nearby
stars, and, second, by subtracting a reference image constructed from
images taken on Mar. 11 between UT 05:26:28.5 and 06:00:53.6 (when the
OT has dropped below our detection threshold). The two methods yield
similar results. From 0.42 to 1.72 hour after the burst, the OT is
observed to decay with a power-law index 0.6+/-0.1, consistent with the
observation by the LBT (Garnavich et al., GCN 7390). The later images
have degraded seeing and don't constrain the time dependence of the OT
very well. The magnitudes reported below are unfiltered calibrated to
SDSS r using standard stars in the pre-burst SDSS observations (Cool et
al., GCN 7396).
Start_UT End_UT mag magerror mlim(of image)
---------------------------------------------------------------
09:03:03.4 09:07:31.2 17.2 0.1 18.4
09:56:17.5 10:09:49.8 18.0 0.1 19.4